In recent years, in order to improve fuel efficiency or reduce exhaust emission, some cars having an internal combustion engine such as an engine include what is called an idling-stop function, in which an engine is automatically stopped while a vehicle stops and a driver operates a brake pedal, and the vehicle is automatically re-started, for example, by a driver's operation for re-start such as decrease in an amount of operation of a brake pedal to zero.
In this idling-stop, the engine may be re-started while an engine speed is relatively high. In such a case, with a conventional starter in which pushing-out of a pinion gear for rotating the engine and rotation of the pinion gear are caused by one drive command, the starter is driven after waiting until the engine speed sufficiently lowers, in order to facilitate engagement between the pinion gear and a ring gear of the engine. Then, a time lag is caused between issuance of a request to re-start an engine and actual engine cranking, and the driver may feel uncomfortable.
In order to solve such a problem, Japanese Patent Laying-Open No. 2005-330813 (Patent Document 1) discloses a technique for causing a pinion gear to perform a rotational operation with the use of a starter configured such that a pinion gear engagement operation and a pinion gear rotational operation can independently be performed prior to the pinion gear engagement operation when a re-start request is issued while rotation of an engine is being lowered immediately after a stop request is generated and for re-starting the engine by causing the pinion gear engagement operation when a pinion gear rotation speed is in synchronization with an engine speed.